Polyester resin and process for its production

ABSTRACT

A polyester resin characterized in that the content of the copolymerized components other than the terephthalic acid component and the ethylene glycol component, is not more than 4 mol % based on the total dicarboxylic acid component, and when polyester resin is formed into a molded product, the molded product has a specific absorbance.

TECHNICAL FIELD

[0001] The present application claims a benefit of Japanese PatentApplication No. 2001-29135, and the content of this application will bereferred to as a reference in the present specification.

[0002] The present invention relates to a polyester resin, whereby amolded product excellent in a gas barrier property and also excellent inan ultraviolet shielding property, a color tone, etc., and which isparticularly suitable for molding a bottle for e.g. a beverage requiredto have an aroma retention property, and further, to a polyester resin,whereby the acetaldehyde content in a molded product is reduced toeliminate an influence over the taste, aroma, etc. of the content, and aprocess for its production, whereby the polycondensability is improved.

BACKGROUND ART

[0003] Heretofore, a polyester resin such as a polyethyleneterephthalate resin has been widely used for packaging containers forvarious beverages, etc., since it is excellent in mechanical strength,chemical stability, gas barrier property, aroma-retention property,hygienics, etc., and is relatively inexpensive and light in weight.Especially, as a container for a beverage which requires heatsterilization filling, for e.g. a fruit juice beverage, a bottle havinga high gas barrier property, etc. imparted by an application of stretchheat setting, has shown a rapid expansion. Such a bottle is produced,for example, by injection molding a bottomed tubular preform, reheatingthe preform to soften it, followed by stretch blow molding. At thattime, the blow mold is heated to apply heat setting to the bottle,whereby crystals of molecular chains aligned by stretching are fixed toprovide the high gas barrier property, etc.

[0004] However, with respect to the polyethylene terephthalate resin tobe used in such a field of beverage containers, in the case of apolyethylene terephthalate resin produced by using an antimony compoundas a polycondensation catalyst, which is most commonly used for bottlesfor wide range of purpose, copolymerizable components such asisophthalic acid, diethylene glycol, etc. other than the terephthalicacid component and the ethylene glycol component, are copolymerized inan amount of from about 3 to 10 mol % based on the total dicarboxylicacid component in order to provide transparency, whereby the intendedgas barrier property may not be obtained, whereby the aroma-retentionproperty as a bottle tends to decrease, and the aroma of the content islikely to decrease, or the ultraviolet shielding property tends to bepoor, whereby the flavor component or the color tone of the content islikely to deteriorate, and further, another problem is also worried suchthat antimony remaining in the resin will elute from the container at ahigh temperature and will transfer to the contained beverage althoughslightly. On the other hand, with a polyethylene terephthalate resinprepared by using a germanium compound as a polycondensation catalyst,which is commonly used for heat resistant bottles, copolymerizablecomponents other than the terephthalic acid component and the ethyleneglycol component, may be copolymerized in a relatively small amount at alevel of more than 2 to 5 mol % based on the total dicarboxylic acidcomponent, but the above-mentioned problem relating to a decrease of thearoma-retention property cannot still be solved, and the ultravioletshielding property is also inferior, and further, the germanium compoundis expensive, whereby an economical disadvantage cannot be avoided.Accordingly, it is strongly desired to have a substitutepolycondensation catalyst developed.

[0005] Further, many polyethylene terephthalate resins have beenproposed which are prepared by using titanium compounds aspolycondensation catalysts, but they have had problems such that theylack in thermal stability, so that the obtainable resins tend to have ayellowish color tone, or the change in the color tone after being heatedis substantial, and further have problems such that acetaldehyde, acyclic trimer, etc. are formed in a large amount as by-products duringthe polycondensation and the melt molding, and when used as bottles,they tend to deteriorate the tastes, aromas, etc. of the containedbeverages. Whereas, e.g. JP-A-8-73581 discloses a process for producinga polyethylene terephthalate resin which is colorless and excellent intransparency, by using a titanium compound, a cobalt compound, and alimited amount of complex-forming agent, such as phosphoric acid,phosphorous acid and/or phosphonic acid or its derivative. However,according to the study conducted by the present inventors, it has beenfound that the polyethylene terephthalate resin obtainable by thisprocess is not one which is able to solve the above-mentioned problemsuch as a decrease in the aroma-retention property and the problem suchas deterioration of the taste, the aroma, etc. of the content.

[0006] Further, EP-A-1013692 discloses that production of acetaldehydeas a by-product during the polycondensation and the melt molding can besuppressed by using titanium and metal compounds, as polycondensationcatalysts, so that specific amounts of titanium atoms and metal atomssuch as magnesium, would be in a specific ratio. Further, inJP-A-2000-339919 filed by the present applicants, it is disclosed thatin the polycondensation in the presence of (1) a titanium compound, (2)a compound of at least one element selected from the group consisting ofmetal elements of Group 1A of the periodic table, elements of Group 2Aof the periodic table and manganese, and (3) a phosphorus compound, theorder of addition of the respective compounds (1), (2) and (3) is set tobe (3), then (2) and then (1), whereby by-products such as acetaldehyde,a cyclic trimer, etc., can be reduced. However, according to the studyby the present inventors, it has been found that these methods arecertainly effective to reduce by-products, but with the disclosedmethods, there is still a room for improvement with respect to the gasbarrier property, the ultraviolet shielding property or thepolycondensability.

[0007] The present invention has been made in view of theabove-described prior art, and it is an object of the present inventionto provide a polyester resin, whereby a molded product excellent in thegas barrier property and also excellent in the ultraviolet shieldingproperty, the color tone, etc., and which is particularly suitable formolding a bottle for e.g. a beverage required to have an aroma-retentionproperty, and further, a polyester resin, whereby the acetaldehydecontent as a molded product is reduced to eliminate an influence overthe taste, the aroma, etc. of the content, and a process for itsproduction, whereby the polycondensability is improved.

DISCLOSURE OF THE INVENTION

[0008] As its gist, the present invention provides a polyester resinproduced by polycondensing a dicarboxylic acid component containingterephthalic acid or its ester-forming derivative as the main component,and a diol component containing ethylene glycol as the main component inthe presence of (1) a compound of at least one member selected from thegroup consisting of titanium group elements in Group 4A of the periodictable, via an esterification reaction or an ester exchange reaction,characterized in that the content of copolymerized components other thanthe terephthalic acid component and the ethylene glycol component, isnot more than 4 mol % based on the total dicarboxylic acid component,and in a molded product with a thickness of 3.5 mm injection-molded at280° C., the difference between the absorbance at a wavelength of 395 nmand the absorbance at a wavelength of 800 nm is at least 0.08, and thedifference between the absorbance at a wavelength of 500 nm and theabsorbance at a wavelength of 800 nm is at most 0.05.

[0009] Further, as its gist, the present invention provides a processfor producing a polyester resin, which comprises polycondensing adicarboxylic acid component containing terephthalic acid or itsester-forming derivative as the main component, and a diol componentcontaining ethylene glycol as the main component in the presence of (1)a compound of at least one member selected from the group consisting oftitanium group elements in Group 4A of the periodic table, (2) acompound of at least one element selected from the group consisting ofmetal elements of Group 1A of the periodic table, elements of Group 2Aof the periodic table, manganese, iron and cobalt, and (3) a phosphoruscompound, via an esterification reaction or an ester exchange reaction,characterized in that the amounts of the respective compounds (1), (2)and (3) are such amounts that their contents will be from 0.02 to 0.2mol as the total amount (T) of atoms of the compound (1), from 0.04 to0.6 mol as the total amount (M) of atoms of the compound (2) and from0.02 to 0.4 mol as the total amount (P) of atoms of the compound (3),per 1 ton of the polyester resin.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1(a): a plan view of a stepped molded plate for evaluation ofthe physical properties, molded in Examples.

[0011]FIG. 1(b): a front view of the stepped molded plate for evaluationof the physical properties, molded in Examples.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] The polyester resin of the present invention is one produced bypolycondensing a dicarboxylic acid component containing terephthalicacid or its ester-forming derivative as the main component, and a diolcomponent containing ethylene glycol as the main component, via anesterification reaction or an ester exchange reaction, and is preferablya polycondensate of a dicarboxylic acid component in which theterephthalic acid component constitutes at least 96 mol %, morepreferably at least 99 mol %, of the total dicarboxylic acid component,with a diol component in which the ethylene glycol component constitutesat least 96 mol %, more preferably at least 97 mol %, of the total diolcomponent. If the proportion of the terephthalic acid component in thetotal dicarboxylic acid component, and the proportion of the ethyleneglycol component in the total diol component, are less than the aboveranges, the aligned crystallization of the molecular chains bystretching at the time of molding a bottle, etc., tends to beinadequate, whereby the mechanical strength, the gas barrier property,the heat resistance, etc., as a molded product such as a bottle, tend tobe inadequate.

[0013] And, in the polyester resin of the present invention, it isessential that the content of copolymerizable components other than theterephthalic acid component and the ethylene glycol component is notmore than 4 mol %, preferably not more than 3 mol %, further preferablynot more than 2 mol %. If the content of copolymerizable componentsexceeds the above range, it tends to be difficult to obtain a moldedproduct which is excellent in e.g. the aroma-retention property, etc.,and in which the acetaldehyde content is reduced.

[0014] Further, the ester-forming derivative of terephthalic acid may,for example, be a C₁₋₄ alkyl ester, a halogenated product, etc. Further,dicarboxylic acid components other than terephthalic acid or itsester-forming derivative, may, for example, be an aromatic dicarboxylicacid such as phthalic acid, isophthalic acid, dibromoisophthalic acid,sodium sulfoisophthalate, phenylene dioxydicarboxylic acid,4,4′-diphenyl dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid,4,4′-diphenyl ketone dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid or2,6-naphthalene dicarboxylic acid, an alicyclic dicarboxylic acid suchas hexahydroterephthalic acid or hexahydroisophthalic acid, and analiphatic dicarboxylic acid such as succinic acid, glutaric acid, adipicacid, pimelic acid, suberic acid, azelaic acid, sebacic acid,undecadicarboxylic acid or dodecacarboxylic acid, as well as a C₁₋₄alkyl ester thereof, and a halogenated product thereof. Among them, inthe present invention, isophthalic acid or its ester-forming derivativeis preferred, and the proportion in the total dicarboxylic acidcomponent is preferably from 0.1 to 3 mol %. If isophthalic acid iswithin this range, the solid phase polycondensation rate is high, andreduction of the acetaldehyde content in a molded product of theobtainable resin tends to be facilitated.

[0015] Further, as the diol component other than ethylene glycol,diethylene glycol formed as a by-product in the reaction system may bementioned, and the proportion of such diethylene glycol in the totaldiol component is preferably not more than 3 mol %, more preferably from1 to 3 mol %, inclusive of one added as a copolymerizable component fromoutside the system. If diethylene glycol exceeds this range, a problemtends to occur such that when the obtainable resin is formed into amolded product, the gas barrier property decreases, or it tends to bedifficult to reduce the acetaldehyde content. Further, other diolcomponents may, for example, be an aliphatic diol such as trimethyleneglycol, tetramethylene glycol, pentamethylene glycol, hexamethyleneglycol, octamethylene glycol, decamethylene glycol, neopentyl glycol,2-ethyl-2-butyl-1,3-propane diol, polyethylene glycol orpolytetramethylene ether glycol, an alicyclic diol such as1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol,1,4-cyclohexanedimethylol or 2,5-norbornanedimethylol, and an aromaticdiol such as xylylene glycol, 4,4′-dihydroxybiphenyl,2,2-bis(4′-hydroxyphenyl)propane,2,2-bis(4′-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone orbis(4-β-hydroxyethoxyphenyl)sulfonic acid, as well as an ethylene oxideadduct or a propylene oxide adduct, of 2,2-bis(4′-hydroxyphenyl)propane.

[0016] Further, copolymerizable components may, for example, be ahydroxycarboxylic acid or an alkoxycarboxylic acid, such as glycolicacid, p-hydroxybenzoic acid or p-β-hydroxyethoxybenzoic acid, a singlefunctional component such as stearyl alcohol, heneycosanol, octacosanol,benzyl alcohol, stearic acid, behenic acid, benzoic acid, t-butylbenzoic acid or benzoylbenzoic acid, and a polyfunctional component withat least trifunctional, such as tricarbarylic acid, trimellitic acid,trimesic acid, pyromellitic acid, naphthalene tetracarboxylic acid,gallic acid, trimethylolethane, trimethylolpropane, glycerol,pentaerythritol or sugar ester.

[0017] The polyester resin of the present invention is such that in amolded product with a thickness of 3.5 mm injection-molded at 280° C.,the difference between the absorbance at a wavelength of 395 nm and theabsorbance at a wavelength of 800 nm is at least 0.08, and thisdifference in absorbance is preferably at least 0.15, more preferably atleast 0.20. If this difference in absorbance is less than the aboverange, it tends to be difficult to obtain a molded product excellent inthe ultraviolet shielding property. Further, in a molded product havinga thickness of 3.5 mm injection-molded at 280° C., the differencebetween the absorbance at a wavelength of 500 nm and the absorbance at awavelength of 800 nm is at most 0.05, and this difference in absorbanceis preferably at most 0.04, more preferably at most 0.03. If thisdifference in absorbance is less than the above range, it tends to bedifficult to obtain a molded product excellent in the color tone. Here,the absorbance of a molded product is a value at each wavelength whenmeasured by means of an ultraviolet visible light absorption photometerwithin a wavelength range of from 300 to 800 nm at a scanning speed of127 nm/min.

[0018] Further, the polyester resin of the present invention is suchthat the temperature-rising crystallization temperature (Tc) of theresin in the molded product after the injection molding at 280° C., ispreferably from 150 to 180° C., more preferably from 155 to 165° C.,particularly preferably from 157 to 164° C. This temperature-risingcrystallization temperature (Tc) relates to the crystallization rate ofthe mouth stopper portion, etc. at the time of molding a bottle, and ifthe temperature-rising crystallization temperature (Tc) is either lessthan the above range or more than the above range, the dimensionalstability at the mouth stopper portion deteriorates as a bottle, and aproblem such as leakage of a gas from the mouth stopper portion ordeterioration of the aroma-retention property, tends to result. Here,the temperature-rising crystallization temperature (Tc) is one obtainedby measuring the crystallization peak temperature observed in thetemperature rise when the temperature was raised from 20° C. to 285° C.at a rate of 20° C./min in a nitrogen stream by means of a differentialscanning calorimeter.

[0019] Further, the polyester resin of the present invention is suchthat the intrinsic viscosity ([η]) is preferably from 0.70 to 0.90 dl/g,more preferably from 0.70 to 0.80 dl/g, as a value measured at 30° C. ina solution in a mixed solvent of phenol/tetrachloroethane (weight ratio:1/1). If the intrinsic viscosity ([η]) is less than the above range, themechanical strength tends to be inadequate as a molded product such as abottle. On the other hand, if it exceeds the above range, themoldability for a bottle or the like tends to deteriorate, and it tendsto be difficult to control production of acetaldehyde, etc. asby-products at the time of the melt molding. Further, as the color tone,the color coordinate value b of the Hunter's color difference formula inthe Lab color system as disclosed in Reference 1 in JIS Z8730, ispreferably not more than 4, more preferably from −5 to 2. If value bexceeds the above range, the color tone tends to be yellowish as amolded product such as a bottle. Further, the cyclic trimer content (CT)is preferably not more than 0.50 wt %, more preferably not more than0.40 wt %. If the cyclic trimer content (CT) exceeds the above range,contamination of the mold tends to occur during molding of a bottle,etc.

[0020] Further, the acetaldehyde content (AA₁) is preferably not morethan 5.0 ppm, more preferably not more than 3.0 ppm. Further, theacetaldehyde content (AA₂) of the resin in a molded product afterinjection-molded at 280° C., is preferably not more than 20 ppm, morepreferably not more than 18 ppm, particularly preferably not more than15 ppm. If the acetaldehyde content (AA₁) and the acetaldehyde content(AA₂) exceed the above ranges, it tends to be difficult to eliminate aninfluence over the taste, the aroma, etc. of the content, as a moldedproduct such as bottle. Further, the haze of a molded product with athickness of 5 mm after the injection molding at 280° C. is preferablynot more than 10%, more preferably not more than 8%.

[0021] And, in the present invention, in order to bring theabove-mentioned content of copolymerizable components, the intrinsicviscosity ([η]), color coordinate value b, the cyclic trimer content(CT), the acetaldehyde content (AA₁), as well as the absorbance of themolded product after the injection molding at 280° C., thetemperature-rising crystallization temperature (Tc), the acetaldehydecontent (AA₂), and the haze, etc. within the above ranges, it isessential that the polycondensation of the polyester resin is carriedout in the presence of (1) a compound of at least one member selectedfrom the group consisting of titanium group elements in Group 4A of theperiodic table. Accordingly, the polyester resin of the presentinvention contains (1) a compound of at least one member selected fromthe group consisting of titanium group elements in Group 4A of theperiodic table.

[0022] Here, (1) the compound of a titanium group element of Group 4A ofthe periodic table, i.e. titanium, zirconium or hafnium, may, forexample, be an oxide, a hydroxide, an alkoxide, an acetate, a carbonate,a oxalate and a halide of such an element. Among compounds of suchelements, a titanium compound is preferred. Specifically, the titaniumcompound may, for example, be a titanium alkoxide such as tetra-n-propyltitanate, tetra-1-propyl titanate, tetra-n-butyl titanate, tetra-n-butyltitanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate,tetraphenyl titanate or tetrabenzyl titanate, a titanium oxideobtainable by the hydrolysis of a titanium alkoxide, a titanium/siliconor zirconium double oxide obtainable by the hydrolysis of a mixture of atitanium alkoxide with a silicon alkoxide or a zirconium alkoxide,titanium acetate, titanium oxalate, titanium potassium oxalate, titaniumsodium oxalate, potassium titanate, sodium titanate, a titanicacid/aluminum hydroxide mixture, titanium chloride, a titaniumchloride/aluminum chloride mixture, titanium bromide, titanium fluoride,potassium hexafluorotitanate, cobalt hexafluorotitanate, manganesehexafluorotitanate, ammonium hexafluorotitanate, or titaniumacetylacetonate. Among them, a titanium alkoxide such as tetra-n-propyltitanate, tetra-1-propyl titanate or tetra-n-butyl titanate, titaniumoxalate or titanium potassium oxalate, is preferred, and tetra-n-butyltitanate is particularly preferred.

[0023] Further, with respect to the polycondensation, from the viewpointof the polycondensability, reduction of by-products such asacetaldehyde, a cyclic trimer, etc. in the obtainable resin and thecolor tone, as well as the absorbance of the molded product, thetemperature-rising crystallization temperature, etc., one polycondensedin the coexistence of (2) a compound of at least one element selectedfrom the group consisting of metal elements of Group 1A of the periodictable, elements of Group 2A of the periodic table, manganese, iron andcobalt, and (3) a phosphorus compound, is preferred. Accordingly, thepolyester resin of the present invention preferably contains (2) thecompound of at least one element selected from the group consisting ofmetal elements of Group 1A of the periodic table, elements of Group 2Aof the periodic table, manganese, iron and cobalt, and (3) thephosphorus compound.

[0024] Here, (2) the compound of at least one element selected from thegroup consisting of metal elements of Group 1A of the periodic table,elements of Group 2A of the periodic table, manganese, iron and cobalt,may, for example, be an oxide, a hydroxide, an alkoxide, an acetate, acarbonate, an oxalate, a halide, etc. of lithium, sodium, potassium,magnesium, calcium, manganese, iron, cobalt, etc. Specifically, it may,for example, be lithium acetate, sodium acetate, potassium acetate,magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesiumacetate, magnesium carbonate, calcium oxide, calcium hydroxide, calciumacetate, calcium carbonate, manganese oxide, manganese hydroxide,manganese acetate, ferric acetate, cobalt formate, cobalt acetate,cobalt oxalate, cobalt carbonate, cobalt bromide or cobaltacetylacetonate. Among them, a magnesium compound or a manganesecompound is preferred. Particularly preferred is a magnesium compound,and magnesium acetate is especially preferred.

[0025] Further, (3) the phosphorus compound may, specifically, be apentavalent phosphorus compound, such as orthophosphoric acid,polyphosphoric acid or a phosphoric acid ester such as trimethylphosphate, triethyl phosphate, tri-n-butyl phosphate, trioctylphosphate, triphenyl phosphate, tricresyl phosphate, tris(triethyleneglycol) phosphate, methyl acid phosphate, ethyl acid phosphate,isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate,dibutyl phosphate, dioctyl phosphate or triethylene glycol acidphosphate, phosphorous acid, hypophosphorous acid, a phosphorous acidester such as trimethyl phosphite, diethyl phosphite, triethylphosphite, trisdodecyl phosphite, trisnonyldecyl phosphite, ethyldiethyl phosphonoacetate or triphenyl phosphite, or a trivalentphosphorus compound such as a metal salt of lithium, sodium, potassium,etc. Among them, a phosphoric acid ester as a pentavalent phosphoruscompound is preferred. Particularly preferred is trimethyl phosphate orethyl acid phosphate.

[0026] In the present invention, the respective amounts of (1) the abovecompound of at least one member selected from the group consisting oftitanium group elements in Group 4A of the periodic table, (2) the abovecompound of at least one element selected from the group consisting ofmetal elements of Group 1A of the periodic table, elements of Group 2Aof the periodic table, manganese, iron and cobalt, and (3) the abovephosphorus compound, used at the time of polycondensation, and therespective contents in the resulting polyester resin, are preferablyfrom 0.002 to 1 mol, more preferably from 0.002 to 0.5 mol, as the totalamount (T) of atoms of the compound (1), preferably from 0.04 to 5 mol,more preferably from 0.04 to 3 mol, as the total amount (M) of atoms ofthe compound (2), and preferably from 0.02 to 4 mol, more preferablyfrom 0.02 to 2 mol, as the total amount (P) of atoms of the compound(3), per 1 ton of the polyester resin.

[0027] When the total amount (T) of atoms of the compound (1), the totalamount (M) of atoms of the compound (2) and the total amount (P) ofatoms of the compound (3) are within the above ranges, the ultravioletshielding properties tend to be excellent. Further, particularly, inorder to reduce the acetaldehyde content in the molded product and toimprove the polycondensability, the total amount (T) of atoms of thecompound (1) is more preferably from 0.02 to 0.2 mol, particularlypreferably from 0.04 to 0.15 mol, the total amount (M) of atoms of thecompound (2) is more preferably from 0.04 to 0.6 mol, particularlypreferably from 0.05 to 0.4 mol, most preferably from 0.1 to 0.3 mol,and the total amount (P) of atoms of the compound (3) is more preferablyfrom 0.02 to 0.4 mol, particularly preferably from 0.1 to 0.3 mol, per 1ton of the polyester resin.

[0028] Further, once the amounts of the respective compounds i.e. (1)the compound of at least one member selected from the group consistingof titanium group elements in Group 4A of the periodic table, (2) thecompound of at least one element selected from the group consisting ofmetal elements of Group 1A of the periodic table, elements of Group 2Aof the periodic table, manganese, iron and cobalt, and (3) thephosphorus compound, satisfy the molar amounts of the above ranges asthe total amount (T) of atoms of the compound (1), as the total amount(M) of atoms of the compound (2), and as the total amount (P) of atomsof the compound (3), it is preferred that the molar ratio [P/T] of thetotal amount (P) of atoms of the compound (3) to the total amount (T) ofatoms of the compound (1) is from 0.1 to 10, more preferably from 1 to7, particularly preferably from 2 to 5, and the molar ratio [M/T] of thetotal amount (M) of atoms of the compound (2) to the total amount (T) ofatoms of the compound (1) is from 0.1 to 10, more preferably from 0.5 to7, particularly preferably from 3 to 5. Further, for a polyester resinparticularly excellent in the ultraviolet shielding property, it ispreferred that the molar ratio [P/M] of the total amount (P) of atoms ofthe compound (3) to the total amount (M) of atoms of the compound (2),is more than 0 to 10, more preferably from 1 to 5, particularlypreferably from 2 to 4, and the molar ratio [P/(T+M)] of the totalamount (P) of atoms of the compound (3) to the sum of the total amount(T) of atoms of the compound (1) and the total amount (M) of atoms ofthe compound (2), is more than 0 to 10, more preferably from 0.5 to 5,particularly preferably from 1 to 3.

[0029] If the molar ratio [P/T] is less than the above range, theobtainable resin tends to be yellowish, and thus the color tone tends todeteriorate. On the other hand, if it exceeds the above range, the meltpolycondensability and the solid phase polycondensability, which will bedescribed hereinafter, tend to deteriorate simultaneously. Further, ifthe above molar ratio [M/T] is less than the above range, the meltpolycondensability and the solid phase polycondensability, which will bedescribed hereinafter, will deteriorate simultaneously, and it tends tobe difficult to reduce the acetaldehyde content in the molded product ofthe resulting resin. On the other hand, if it exceeds the above range,the solid phase polycondensability which will be described hereinafter,tends to deteriorate.

[0030] Further, in the present invention, during the polycondensation,metal compounds other than the above-mentioned respective compounds, maybe present within a range not to impair the effects of the presentinvention, and accordingly, such metal compounds may be contained in thepolyester resin of the present invention. In such a case, the metalcompounds may, for example, be compounds such as oxides, hydroxides,alkoxides, carbonates, phosphates, carboxylates or halides of aluminum,chromium, nickel, copper, zinc, germanium, molybdenum, silver, tin,lanthanum, cerium, tungsten, gold, etc. The above-mentioned respectivecompounds and other compounds are preferably ones soluble in water or analcohol such as ethylene glycol.

[0031] The polyester resin of the present invention is produced bypolycondensing a dicarboxylic acid component containing the aboveterephthalic acid or its ester-forming derivative as the main componentand a diol component containing ethylene glycol as the main component inthe presence of (1) the compound of at least one element selected fromthe group consisting of titanium group elements of Group 4A of theperiodic table, preferably in the coexistence of (2) the compound of atleast one element selected from the group consisting of metal elementsof Group 1A of the periodic table, elements of Group 2A of the periodictable, manganese, iron and cobalt, and (3) the phosphorus compound, viaan esterification reaction or an ester exchange reaction, but basicallyin accordance with a common process for producing a polyester resin.Namely, it is produced by introducing into a slurry preparation tank theabove dicarboxylic acid component containing the above terephthalic acidor its ester-forming derivative as the main component and the diolcomponent containing ethylene glycol as the main component together withoptional copolymerizable components, etc., followed by mixing withstirring to obtain a raw material slurry, subjecting it to anesterification reaction for from about 1 to 10 hours in anesterification reactor under atmospheric pressure or elevated pressureunder heating with stirring or to an ester exchange reaction in thepresence of an ester exchange catalyst, then transferring the obtainedpolyester low molecular weight product as the esterification reactionproduct or the ester exchange reaction product to a polycondensationtank, and melt polycondensing it in the presence of the above-mentionedcompounds under atmospheric pressure or gradually reduced pressure underheating with stirring for about 1 to 20 hours. These operations may becarried out by a continuous system or by a batch system.

[0032] At that time, preparation of the raw material slurry comprisingthe dicarboxylic acid component containing terephthalic acid or itsester-forming derivative as the main component and the diol componentcontaining ethylene glycol as the main component, is carried outpreferably by adjusting the molar ratio of the total diol component tothe total dicarboxylic acid component to be within a range of from 1.0to 2.5, more preferably within a range of from 1.03 to 1.7.

[0033] Further, the esterification reaction is carried out by means of asingle esterification reactor or a multi-stage reaction apparatus havinga plurality of esterification reactors connected in series, under refluxof ethylene glycol, while removing water formed by the reaction andexcess ethylene glycol out of the system. At that time, theesterification ratio (the proportion of the esterified by a reactionwith the diol component among the total carboxyl groups of the rawmaterial dicarboxylic acid component) of the polyester low molecularweight product as the esterification reaction product or the esterexchange reaction product, is preferably at least 95%. Further, thenumber average molecular weight of the low molecular weight product ispreferably from 500 to 5,000. Further, in the case of the ester exchangereaction, it is necessary to employ an ester exchange catalyst, wherebythe transparency of the resulting resin usually tends to be poor.Accordingly, in the present invention, the product is preferably oneproduced via the esterification reaction.

[0034] With respect to the reaction conditions in the esterificationreaction, in the case of a single esterification reactor, thetemperature is usually at a level of from 240 to 280° C., the relativepressure to the atmosphere is usually at a level of from 0 to 400 kPa(from 0 to 4 kg/cm²G), and the reaction time is from about 1 to 10 hourswith stirring. In the case of a plurality of esterification reactors,the reaction temperature in the esterification reactor for the firststage is usually from 240 to 270° C., preferably from 245 to 265° C.,and the relative pressure to the atmospheric pressure is usually from 5to 300 kPa (from 0.05 to 3 kg/cm²G), preferably from 10 to 200 kPa (from0.1 to 2 kg/cm²G), and the reaction temperature in the final stage isusually from 250 to 280° C., preferably from 255 to 275° C., and therelative pressure to the atmospheric pressure is usually from 0 to 150kPa (from 0 to 1.5 kg/cm²G), preferably from 0 to 130 kPa (from 0 to 1.3kg/cm²G). Further, the esterification ratio in each stage is preferablyadjusted so that its increase will be equal.

[0035] Further, in the esterification reaction, it is possible tosuppress production of diethylene glycol as a by-product from ethyleneglycol, by adding a small amount of e.g. a tertiary amine such astriethylamine, tri-n-butylamine or benzyl dimethylamine, a quaternaryammonium hydroxide such as tetraethylammonium hydroxide,tetra-n-butylammonium hydroxide or trimethylbenzylammonium hydroxide, ora basic compound such as lithium carbonate, sodium carbonate, potassiumcarbonate or sodium acetate.

[0036] Further, the melt polycondensation is carried out under reducedpressure, while distilling off formed ethylene glycol out of the system,by means of a single melt polymerization tank, or a multi-stage reactionapparatus having a plurality of melt polycondensation tanks connected inseries, for example, an apparatus comprising a perfect mixing typereactor equipped with stirring vanes for the first stage and horizontalplug flow type reactors equipped with stirring vanes for the second andthird stages.

[0037] With respect to the reaction conditions in the meltpolycondensation, in the case of a single polycondensation tank, thetemperature is usually from about 250 to 290° C., the pressure isgradually reduced from the atmospheric pressure, so that finally, theabsolute pressure will be usually at a level of from 1.3 to 0.013 kPa(from 10 to 0.1 Torr), and the reaction time is from about 1 to 20 hourswith stirring. Whereas, in the case of a plurality of polycondensationtanks, the reaction temperature in the polycondensation tank for thefirst stage is usually from 250 to 290° C., preferably from 260 to 280°C. and the absolute pressure is usually from 65 to 1.3 kPa (from 500 to10 Torr), preferably from 26 to 2 kPa (from 200 to 15 Torr), and thereaction temperature in the final stage is usually from 265 to 300° C.,preferably from 270 to 295° C., and the absolute pressure is usuallyfrom 1.3 to 0.013 kPa (from 10 to 0.1 Torr), preferably from 0.65 to0.065 kPa (from 5 to 0.5 Torr). The reaction conditions for anintermediate stage are selected to be intermediate conditions thereof,and for example, in a three stage reaction apparatus, the reactiontemperature in the second stage is usually from 265 to 295° C.,preferably from 270 to 285° C., and the absolute pressure is usuallyfrom 6.5 to 0.13 kPa (from 50 to 1 Torr), preferably from 4 to 0.26 kPa(from 30 to 2 Torr).

[0038] Further, at the time of polycondensation, timing for addition of(1) the compound of at least one element selected from the groupconsisting of titanium group elements of Group 4A of the periodic table,(2) the compound of at least one element selected from the groupconsisting of metal elements of Group 1A of the periodic table, elementsof Group 2A of the periodic table, manganese, iron and cobalt, and (3)the phosphorus compound, to the reaction system, may be at any one of anoptional stage of a step of preparing a slurry of the starting materialterephthalic acid or its ester-forming derivative, ethylene glycol, andoptionally employed other dicarboxylic acid components, or a step of theesterification reaction or the ester exchange reaction, or in theinitial stage of the melt polycondensation step. However, the compounds(1) and (2) are added preferably in the step of the esterificationreaction or the ester exchange reaction, or in the stage oftransportation to the melt polycondensation step, and it is alsopreferred that they are added at a stage where the esterification ratioof the esterification reaction product or the ester exchange reactionproduct reaches at least 90%. Further, it is preferred that the compound(1) is added later than the compound (2). Further, it is preferred thatthe compound (3) is added at a stage where the esterification ratio ofthe esterification reaction product or the ester exchange reactionproduct is less than 90%.

[0039] With respect to the specific steps for addition of the respectivecompounds, it is preferred, for example, that the compound (1) is addedto the esterification reaction tank for the final stage in themulti-stage reaction apparatus or to the esterification reaction productor the ester exchange reaction product in the stage for transportationto the melt polycondensation step, and the compound (2) is added to theesterification reaction tank for the final stage in the multi-stagereaction apparatus. Further, the compound (3) is preferably added to theslurry preparation tank or the esterification reaction tank for thefirst stage, particularly preferably to the slurry preparation tank.Namely, in the present invention, it is preferred to set the order ofaddition of the respective compounds (1), (2) and (3) to the reactionsystem to be (3) then (2) and then (3).

[0040] By setting the timing of addition and the order of addition ofthe respective compounds (1), (2) and (3) to the reaction system asmentioned above, the thermal stability of the resin can be improved, andproduction of diethylene glycol as a by-product in the reaction systemwhich causes production of acetaldehyde, etc. as by-products during themelt molding, can be suppressed, and further, it is possible toeffectively obtain the effects for improving the melt polycondensabilityand the solid phase polycondensability.

[0041] Further, addition of the respective compounds (1), (2) and (3) tothe reaction system at the time of the polycondensation, is preferablycarried out in the form of a solution in e.g. water or an alcohol suchas ethylene glycol. In an ethylene glycol solution in a case where atitanium compound is used as the compound (1), it is preferred to adjustthe concentration of titanium atoms to be from 0.01 to 0.3 wt % and thewater concentration to be from 0.1 to 1 wt %, from the viewpoint of thedispersibility of the titanium compound in the reaction system and theimprovement of the melt polycondensability and the solid phasepolycondensability thereby obtainable.

[0042] Further, the reaction time for the melt polycondensation isusually preferably at most 3.5 hours. If the reaction time exceeds it,it tends to be difficult to reduce the aldehyde content in the resultingresin and the amount of acetaldehyde by-product during the melt molding.

[0043] The polyester resin obtainable by the above melt polycondensationis such that the intrinsic viscosity ([η₁]) is preferably from 0.35 to0.75 dl/g, more preferably from 0.50 to 0.60 dl/g, as a value measuredat 30° C. in a solution in a mixed solvent of phenol/tetrachloroethane(weight ratio: 1/1). If the intrinsic viscosity ([η₁]) is less than theabove range, the withdrawing property from the polycondensation tank,which will be described hereinafter, tends to be poor. On the otherhand, if it exceeds the above range, it tends to be difficult to reducethe acetaldehyde content in the resulting resin. Further, the meltpolycondensation velocity (V₁) as a value obtained by dividing theabove-mentioned intrinsic viscosity ([η₁]) of the resulting polyesterresin by the above-mentioned reaction time, is preferably at least 0.15dl/g/hr.

[0044] Further, the resin obtained by the melt polycondensation isusually withdrawn in the form of a strand from a discharge outletprovided at the bottom of the polycondensation tank and, while beingcooled by water or after being cooled by water, cut by a cutter intoparticles such as pellets or chips. Further, such particles after themelt polycondensation, are usually heated at a temperature of from about60 to 180° C. in an atmosphere of an inert gas such as nitrogen, carbondioxide or argon, or in a steam atmosphere, or in a steam-containinginert gas atmosphere, to crystallize the surface of the resin particlesand then subjected to solid phase polycondensation by heat treatment ata low temperature of from immediately below the adhesive temperature ofthe resin to 80° C. in an inert gas atmosphere or/and under a reducedpressure of from 1.3 to 0.013 kPa (from 10 to 0.1 Torr), usually for aperiod of at most 50 hours, while letting the particles flow not to fuseone another. By this solid phase polycondensation, it is possible tofurther increase the polymerization degree and to reduce by-productssuch as acetaldehyde, a cyclic trimer, etc.

[0045] The polyester resin obtainable by the above solid phasepolycondensation is such that the intrinsic viscosity ([η₂]) ispreferably from 0.70 to 0.90 dl/g, more preferably from 0.70 to 0.80dl/g, as a value measured at 30° C. in a solution in a mixed solvent ofphenol/tetrachloroethane (weight ratio: 1/1). Further, the solid phasepolycondensation velocity (V₂) as a value obtained by dividing thedifference ([η₂]−[η₁]) between the above intrinsic viscosity ([η₂]) ofthe obtainable solid phase polycondensation resin and the intrinsicviscosity ([η₁]) of the above-mentioned melt polycondensation resin, bythe above-mentioned reaction time, is preferably from 0.008 to 0.015dl/g/hr. Further, the ratio (V₂/V₁) of this solid phase polycondensationvelocity to the above-mentioned melt polycondensation velocity ispreferably within a range of from 0.04 to 0.07, more preferably within arange of from 0.05 to 0.07.

[0046] Further, for the purpose of improving the thermal stability,reduction of by-products such as acetaldehyde, a cyclic trimer, etc.during the molding, etc., the resin obtained by the above meltpolycondensation or the solid phase polycondensation may usually besubjected to water treatment of dipping it in warm water of at least 40°C. for at least 10 minutes, or steam treatment of contacting it withsteam or a steam-containing gas of at least 60° C. for at least 30minutes, or treatment with an organic solvent, an acidic aqueoussolution of e.g. various mineral acids, organic acids or phosphoricacids, or treatment by an alkaline aqueous solution or an organicsolvent solution, of a Group 1A metal, a Group 2A metal or an amine.

[0047] Further, the polyester resin of the present invention may containa crystalline thermoplastic resin different from the polyester resin ina content of from 0.0001 to 1,000 ppm, preferably from 0.0005 to 100ppm, more preferably from 0.001 to 10 ppm, as the case requires, toadjust the temperature-rising crystallization temperature (Tc) of theresin in the above-mentioned molded product after injection molding tothe above-mentioned range. As such a crystalline thermoplastic resin, apolyolefin resin or a polyamide resin may be mentioned as a typicalexample.

[0048] The polyolefin resin may, for example, be a homopolymer of ana-olefin having from about 2 to 8 carbon atoms, such as ethylene,propylene or butene-1, or a copolymer of such an α-olefin with anotherα-olefin having from 2 to 20 carbon atoms such as ethylene, propylene,1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene,1-octene or 1-decene, or with a vinyl compound such as vinyl acetate,acrylic acid, methacrylic acid, an acrylate, a methacrylate, vinylchloride or styrene. Specifically, it may, for example, be an ethyleneresin such as an ethylene homopolymer such as a low, intermediate orhigh density polyethylene, an ethylene/propylene copolymer, anethylene/1-butene copolymer, an ethylene/4-methyl-1-pentene copolymer,an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, anethylene/vinyl acetate copolymer, an ethylene/acrylic acid copolymer, anethylene/methacrylic acid copolymer or an ethylene/ethyl acrylatecopolymer, a propylene resin such as a propylene homopolymer, apropylene/ethylene copolymer or a propylene/ethylene/1-butene copolymer,and a 1-butene resin such as a 1-butene homopolymer, a 1-butene/ethylenecopolymer or a 1-butene/propylene copolymer.

[0049] Further, the polyamide resin may, for example, be a polymer of alactam such as butyrolactam, δ-valerolactam, ε-caprolactam,enantholactam or ω-lauryllactam, a polymer of an amino acid such as6-amino caproic acid, 7-amino heptanoic acid, 8-amino octanoic acid,9-amino nonanoic acid, 11-amino undecanoic acid or 12-amino dodecanoicacid, a polycondensate of a diamine, such as an aliphatic diamine suchas 1,4-butane diamine, 1,5-pentane diamine, 1,5-hexane diamine,1,6-hexane diamine, 1,9-nonane diamine, 1,11-undeca diamine,1,12-dodecane diamine or α,ω-diaminopolypropylene glycol, an alicyclicdiamine such as 1,3- or 1,4-bis(aminomethyl)cyclohexane orbis(p-aminocyclohexylmethane), or an aromatic diamine such as m- orp-xylylene diamine, with a dicarboxylic acid, such as an aliphaticdicarboxylic acid such as glutaric acid, adipic acid, suberic acid,sebacic acid or dodecanoic diacid, an alicyclic dicarboxylic acid suchas cyclohexane dicarboxylic acid, or an aromatic dicarboxylic acid suchas terephthalic acid or isophthalic acid, or a copolymer thereof.Specifically, for example, nylon 4, nylon 6, nylon 7, nylon 8, nylon 9,nylon 11, nylon 12, nylon 66, nylon 69, nylon 610, nylon 611, nylon 612,nylon 6T, nylon 6I, nylon MXD6, nylon 6/66, nylon 6/610, nylon 6/12,nylon 6/6T or nylon 6I/6T may be mentioned.

[0050] In the present invention, the above crystalline thermoplasticresin may be incorporated to the polyester resin by a common method suchas a method of directly adding and melt mixing or a method of adding andmelt mixing as a master batch the above crystalline thermoplastic resinto the above polyester resin so that its content becomes within theabove-mentioned range. Otherwise, a method may be employed wherein theabove crystalline thermoplastic resin is directly added as a powder at aproduction stage of the above polyester resin, for example, at any stageof e.g. during the melt polycondensation (the starting materials,slurry, catalyst, etc.), immediately after the melt polycondensation,immediately after the preliminary crystallization, during the solidphase polycondensation or immediately after the solid phasepolycondensation, or during a period after the production stage untilthe molding stage, or a liquid such as water having the powder dispersedtherein, is contacted with the polyester resin chips, a gas such as airhaving the powder included, is contacted with the polyester resin chips,or the polyester resin chips are contacted to a component made of thecrystalline thermoplastic resin under a flowing condition, followed bymelt kneading. Among the latter methods, a method is preferred in whichthe crystalline thermoplastic resin is incorporated to air for pneumatictransportation at the time of pneumatic transportation to a preliminarycrystallization machine or at the time of pneumatic transportation to asolid polycondensation tank, of chips of the polyester resin after themelt polycondensation, or at the time of pneumatic transportation to astorage tank or at the time of pneumatic transportation to a moldingmachine, of chips after the solid phase polycondensation.

[0051] Further, in the present invention, the polyester resin maycontain, for example, an ultraviolet absorber of e.g. a benzophenonetype such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone,2,2′-dihydroxy-4-methoxybenzophenone or2,2′-dihydroxy-4,4′-dimethoxybenzophenone, a benzotriazole type such as2-(2′-hydroxy-5′-methylphenyl)benzotriazole,2-(2′-hydroxy-5′-butylphenyl)benzotriazole,2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-t-amylphenyl)benzotriazole,2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole or2-(2′-hydroxy-3′,5′-di-t-butylphenyl)-5-chlorobenzotriazole, asalicylate type such as phenyl salicylate, p-t-butylphenyl salicylate orp-octylphenyl salicylate, or a cyanoacrylate type such as2-ethylhexyl-2-cyano-3,3′-diphenylacryalte, and an antioxidant, aphotostabilizer, an antistatic agent, a lubricant, a blocking preventiveagent, an antifogging agent, a nucleating agent, a plasticizer, acolorant, a filler, etc.

[0052] The polyester resin of the present invention may, for example, bemolded into a preform by injection molding, followed by stretch blowmolding, or molded into a parison by extrusion, followed by blowmolding, to obtain a bottle or the like, or it may be formed into asheet by extrusion, followed by heat forming to obtain a tray, acontainer or the like, or said sheet may be biaxially stretched toobtain a film or the like, which will be particularly useful in thefield of packaging beverage products. Among them, it is particularlysuitable for molding the preform obtained by injection molding into abottle by a biaxially stretching blow molding method, and it issuitable, for example, for a container for e.g. a carbonated beverage,an alcoholic beverage, or a liquid seasoning such as soy sauce, aregular sauce, Japanese sweet rice wine for cooking or dressing, orafter heat setting, for a container which is required to have anaroma-retention property and an ultraviolet shielding property and whichis required to be free from an influence over the taste, fragrance,etc., of a beverage such as a fruit juice beverage, a vitamin beverage,a flavor tea or mineral water.

[0053] Now, the present invention will be described in further detailwith reference to Examples. However, the present invention is by nomeans restricted by the following Examples.

EXAMPLE 1

[0054] Slurries of 43 kg (260 mol) of terephthalic acid and 19 kg (312mol) of ethylene glycol were continuously supplied over a period of 4hours to an esterification reaction tank having about 60 kg ofbis(hydroxyethyl) terephthalate previously charged and maintained at atemperature of 250° C. and a pressure of 1.2×10⁵ Pa, and even aftercompletion of the supply, the esterification reaction was furthercarried out for one hour. About one half of this esterification reactionproduct was transferred to a polycondensation tank.

[0055] Then, to the polycondensation tank to which the esterificationreaction product was transferred, from its pipe, ethyl acid phosphate,magnesium acetate and tetra-n-butoxy titanium were sequentially added intheir ethylene glycol solutions, respectively, with intervals of 5minutes, so that 0.387 mol of phosphorus atoms (P), 0.062 mol ofmagnesium atoms (Mg) and 0.063 mol of titanium atoms (Ti) would remainper 1 ton of the resulting polyester resin. Then, the interior of thesystem was heated from 250° C. to 280° C. over a period of 2 hours and30 minutes, and at the same time, the pressure was reduced from normalpressure to 4×10² Pa over a period of one hour, and while maintainingthe same pressure, melt polycondensation was carried out for a period oftime until the intrinsic viscosity of the obtained resin became 0.55dl/g. The polymer was withdrawn in the form of a strand from thedischarge outlet provided at the bottom of the polycondensation tank,cooled with water and then cut into chips to obtain about 50 kg of apolyethylene terephthalate resin.

[0056] Then, the obtained polyester resin chips were continuouslysupplied into an agitation crystallizer maintained at about 160° C. sothat the retention time would be about 5 minutes, for crystallization,then dried at 160° C. for 2 hours in a nitrogen stream of 40 l/min in aninert oven (“IPHH-201 model”, manufactured by ESPEC), and heated at 210°C. for a period of time until the intrinsic viscosity became 0.74 dl/g,for solid phase polycondensation.

[0057] With respect to the obtained polyester resin chips, the contentsof copolymerizable components, the contents of metal atoms of therespective metal compounds, the intrinsic viscosity ([η]), the colorcoordinate value b as the color tone and the cyclic trimer content (CT)were measured by the following methods, and the results are shown inTable 1.

[0058] Content of Copolymerizable Component

[0059] With respect to a solution having a resin sample dissolved at aconcentration of 3 wt % in a mixed solvent of deuteratedchloroform/hexafluoroisopropanol (weight ratio: 7/3), ¹H-NMR wasmeasured by a nuclear magnetic resonance apparatus (“JNM-EX270 model”,manufactured by Nippon Denshi K.K.), and the respective peaks wereidentified, whereupon from the integral value of a peak, the content ofthe copolymerizable component was calculated.

[0060] Contents of Metal Atoms

[0061] 2.5 g of a resin sample was ashed and completely decomposed byhydrogen peroxide in the presence of sulfuric acid in accordance with ausual method and then adjusted by distilled water to a constant volumeof 50 ml, and with respect to this sample, quantitative analysis wascarried out by means of a plasma emission spectrometer (ICP-AES “JY46Pmodel”, manufactured by JOBIN YVON COMPANY), whereupon the molar amountper 1 ton of the polyester resin was calculated.

[0062] Intrinsic Viscosity ([η])

[0063] 0.25 g of a freeze-pulverized resin sample was dissolved at aconcentration (c) of 1.0 g/dl in a mixed solvent ofphenol/tetrachloroethane (weight ratio: 1/1), at 110° C. for 30 minutesin the case of a melt polycondensate resin, or at 120° C. for 30 minutesin the case of a solid phase polycondensate resin, whereupon by means ofan Ubbellohde capillary viscometer, the relative viscosity (η rel) tothe solvent was measured at 30° C. A ratio (η sp/c) of the specificviscosity (η sp) obtained from this relative viscosity (η rel)-1, to theconcentration (c), was obtained. In a similar manner, the correspondingratios (η sp/c) were obtained when the concentration (c) was changed to0.5 g/dl, 0.2 g/dl and 0.1 g/dl, respectively. From these values, aratio (η sp/c) when the concentration (c) was extrapolated to be 0, wasobtained as the intrinsic viscosity [η] (dl/g)

[0064] Color Tone

[0065] A resin sample was filled into a cylindrical powder calorimetriccell having an inner diameter of 36 mm and a depth of 15 mm to be flush,and by means of a calorimetric color difference meter (“ND-300A”,manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD.), color coordinateb of the Hunter's color difference formula in the Lab color system asdisclosed in Reference 1 of JIS Z8730, was obtained as a simple averagevalue of values measured at four positions by rotating the cell every90° by a reflection method.

[0066] Cyclic Trimer Content (CT)

[0067] 4.0 mg of a resin sample was accurately weighted and dissolved in2 mΩ of a mixed solvent of chloroform/hexafluoroisopropanol (volumeratio: 3/2), and then further diluted by an addition of 20 ml ofchloroform. Then, 10 ml of methanol was added thereto forreprecipitation, followed by filtration to obtain a filtrate, which wasevaporated to dryness. Then, the residue was dissolved in 25 ml ofdimethylformamide. The amount of a cyclic trimer (cyclotriethyleneterephthalate) in this solution was quantitatively analyzed by liquidchromatography (“LC-10A”, manufactured by Shimadzu Corporation).

[0068] Then, the obtained resin was dried at 160° C. for at least 16hours in a vacuum dryer (“DP-41 model”, manufactured by YAMATO CHEMICALINDUSTRY CO., LTD). Then, by an injection molding machine (“M-70AII-DM”,manufactured by Meiki Co., Ltd.), a stepped molded plate having theshape as shown in FIG. 1 and having a size of 50 mm×100 mm andthicknesses of six steps ranging from 6 mm to 3.5 mm in a transversedirection with each step being 0.5 mm, was injection-molded at acylinder temperature of 280° C. under a back pressure of 5×10⁵ Pa at aninjection rate of 40 cc/sec under a dwell pressure of 35×10⁵ Pa at amold temperature of 25° C. and with a molding cycle of about 75 seconds.Further, in FIG. 1, G indicates a gate portion.

[0069] With respect to the molded plate thus obtained, the absorbance ata wavelength of 395 nm and 500 nm, and the temperature-risingcrystallization temperature (Tc) were measured by the following methods,and the results are shown in Table 1.

[0070] Absorbance

[0071] The portion having a thickness of 3.5 mm (portion A+B in FIG. 1)in the molded plate, was measured by means of a ultraviolet visiblelight spectrophotometer (“UV-2400”, manufactured by ShimadzuCorporation) at a scanning speed adjusted to be a low speed mode (127nm/min within a wavelength range of from 300 to 800 nm with a slit widthof 5 nm at a sampling pitch of 0.5 nm by a transmission mode, wherebythe differences from the absorbance at a wavelength of 800 nm, of theabsorbances at wavelengths of 395 nm and 500 nm, were obtained.

[0072] Temperature-Rising Crystallization Temperature (Tc)

[0073] The forward end portion (portion A in FIG. 1) having a thicknessof 3.5 mm in the molded plate, was cut out and dried at 40° C. for 3days by a vacuum dryer, whereupon a sample cut out from the non-surfaceportion was used, and about 10 mg thereof was accurately weighed andsealed in by means of an aluminum oven pan and a pan cover (normalpressure type, “P/N SSC000E030” and “P/N SSC000E032”, manufactured bySeiko Denshi K.K.). By means of a differential scanning calorimeter(“DSC220C”, manufactured by Seiko K.K.), the sample was heated from 20°C. to 285° C. at a rate of 20° C./min in a nitrogen stream, and thecrystallization peak temperature observed during the temperature rise,was measured.

[0074] Separately, the obtained polyester resin chips were dried at 130°C. for 10 hours by a vacuum dryer. Then, by an injection molding machine(“FE-80S”, manufactured by Nissei Plastic Industrial Co., Ltd.), apreform of a test tube shape having an outer diameter of 29.0 mm, aheight of 165 mm, an average wall thickness of 3.7 mm and a weight of 60g, was injection-molded at a cylinder temperature of 280° C. under aback pressure of 5×10⁵ Pa at an injection rate of 45 cc/sec under adwell pressure of 30×10⁵ Pa at a mold temperature of 20° C. with amolding cycle of about 40 seconds.

[0075] Such preforms were heated for 70 seconds in a near infrared rayirradiation furnace equipped with a quartz heater, then left at roomtemperature for 25 seconds and then introduced into a blow mold set at160° C. and subjected to blow molding under a blow pressure of about7×10⁵ Pa for one second and then under a blow pressure of about 30×10⁵Pa for 40 seconds for heat setting, while stretching it in the heightdirection by a stretching rod, followed by cooling in air to obtain 500bottles having an outer diameter of about 95 mm, a height of about 305mm, an average wall thickness of the body portion of about 0.37 mm, aweight of about 60 g and an internal capacity of about 1.5 l. Withrespect to the obtained 498th to 500th bottles, the aroma-retentionproperty was measured and evaluated by the following method, and theresults are shown in Table 1.

[0076] Aroma-Retention Property

[0077] In a bottle, a 100% orange juice was filled in a hot state,tightly sealed with a cap and stored at 10° C. for one month, whereuponthe cap was removed, and the aroma was subjected to a sensory test bycomparing it with a case where the orange juice was stored under thesame conditions in a glass bottle, whereby evaluation was made under thefollowing standards.

[0078] ◯: there was no difference in aroma from the glass bottle, andthe aroma-retention property was good.

[0079] Δ: the aroma was weak as compared with the glass bottle, and thearoma-retention property was slightly poor.

[0080] X: the aroma was extremely weak as compared with the glassbottle, and the aroma-retention property was inferior.

[0081] Further, with respect to the obtained 491st to 500th bottles, thesurface appearance of the body portion of each bottle was visuallyobserved and evaluated under the following standards, to evaluate themold contamination, and the results are shown in Table 1.

[0082] ⊚: the surface was smooth, and no mold contamination wasobserved.

[0083] ◯: the surface smoothness was slightly inferior, and accordingly,the mold contamination was slightly observed but was not practicallyproblematic.

[0084] X: the surface was roughened, deposition of foreign matters wasobserved, and the mold contamination was substantial.

EXAMPLES 2 to 6

[0085] The operation was carried out in the same manner as in Example 1except that the amounts of ethyl acid phosphate, magnesium acetate andtetra-n-butoxy titanium at the time of the melt polycondensation werechanged as shown in Table 1, and then results are shown in Table 1.

EXAMPLE 7

[0086] The operation was carried out in the same manner as in Example 2except that the solid phase polycondensation polyester resin obtained inExample 2 was further subjected to water treatment by immersing it inhot water of 90° C. for two hours, and the results are shown in Table 1.

EXAMPLE 8

[0087] The operation was carried out in the same manner as in Example 7except that the polyester resin obtained in Example 7 was used, and alow density polyethylene was added at the time of the injection moldingof the stepped molding plate and at the time of the injection molding ofthe preform, and the results are shown in Table 1.

COMPARATIVE EXAMPLE 1

[0088] The operation was carried out in the same manner as in Example 1except that at the time of the melt polycondensation, ethyl acidphosphate, magnesium acetate and antimony trioxide were sequentiallyadded in their ethylene glycol solutions, respectively, with intervalsof 5 minutes, and the respective amounts were adjusted as shown in Table1, and the results are shown in Table 1.

COMPARATIVE EXAMPLE 2

[0089] The operation was carried out in the same manner as in Example 1except that at the time of the melt polycondensation, orthophosphoricacid and germanium dioxide were sequentially added in their ethyleneglycol solutions, respectively, with intervals of 5 minutes, and therespective amounts were adjusted as shown in Table 1, and the resultsare shown in Table 1.

COMPARATIVE EXAMPLE 3

[0090] The operation was carried out in the same manner as inComparative Example 2 except that the amount of germanium dioxide waschanged, and the obtained solid phase polycondensation polyester resinwas further subjected to water treatment by dipping it in hot water at90° C. for 4 hours, and the results are shown in Table 1.

COMPARATIVE EXAMPLE 4

[0091] The operation was carried out in the same manner as in Example 1except that at the time of the melt polycondensation, tetra-n-butoxytitanium, magnesium acetate and ethyl acid phosphate were sequentiallyadded in their ethylene glycol solutions, respectively, with intervalsof 5 minutes, and the respective amounts were adjusted as shown in Table1, and the results are shown in Table 1. TABLE 1 Examples 1 2 3 4 5 6 78 Copolymerizable Diethylene glycol 1.8 1.7 1.8 1.6 1.6 1.7 1.7 1.7components (mol % based on dial) Contents of Titanium atoms (T) (mol/t)0.063 0.063 0.063 0.063 0.063 0.125 0.063 0.063 metal atoms Magnesiumatoms (M) (mol/t) 0.062 0.123 0.247 0.123 0.123 0.247 0.123 0.123Germanium atoms (Ge) (mol/t) Antimony atoms (Sb) (mol/t) Phosphorusatoms (P) (mol/t) 0.387 0.387 0.387 0.194 0.065 0.387 0.387 0.387 P/T(mol/mol) 6.14 6.14 6.14 3.08 1.03 3.10 6.14 6.14 M/T (mol/mol) 0.981.95 3.92 1.95 1.95 1.98 1.95 1.95 P/M (mol/mol) 6.24 3.15 1.57 1.580.53 1.57 3.15 3.15 P/(T + M) (mol/mol) 3.10 2.08 1.25 1.04 0.35 1.042.08 2.08 Resin chips Intrinsic viscosity [η] (dl/g) 0.74 0.75 0.75 0.730.74 0.74 0.75 0.75 Color coordinate b +2.6 +1.8 +2.4 +2.4 +3.4 +4.7+1.8 +1.8 Cyclic trimer (wt %) 0.29 0.32 0.33 0.29 0.27 0.22 0.32 0.32content (CT) Stepped molded Absorbance 395 nm 0.16 0.11 0.15 0.14 0.190.26 0.11 0.11 plate 500 nm 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02Temperature-rising (° C.) 165 166 165 172 178 165 164 161crystallization temperature (Tc) Bottle Aroma-retention property ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ Mold contamination property ◯ ◯ ◯ ◯ ◯ ◯ ⊚ ⊚ Comparative Example1 2 3 4 Copolymerizable Diethylene glycol 3.5 2.5 2.5 3.8 components(mol % based on dial) Contents of Titanium atoms (T) (mol/t) 1.086 metalatoms Magnesium atoms (Mg) (mol/t) 2.057 2.180 Germanium atoms (Ge)(mol/t) 0.551 0.716 Antimony atoms (Sb) (mol/t) 1.372 Phosphorus atoms(P) (mol/t) 2.906 0.969 0.969 0.549 P/T (mol/mol) — — — 0.5 M/T(mol/mol) — — — 2.00 P/M (mol/mol) 1.41 — — 0.25 P/(T + M) (mol/mol) — —— 0.17 Resin chips Intrinsic viscosity [η] (dl/g) 0.78 0.76 0.76 0.75Color coordinate b +0.8 +0.9 +1.2 +14.3 Cyclic trimer (wt %) 0.40 0.420.32 0.34 content (CT) Stepped molded Absorbance 395 nm 0.04 0.06 0.050.42 plate 500 nm 0.01 0.01 0.01 0.06 Temperature-rising (° C.) 142 168166 153 crystallization temperature (Tc) Bottle Aroma-retention propertyX Δ Δ X Mold contamination property ◯ ◯ ⊚ X

EXAMPLE 9

[0092] Using a continuous polymerization apparatus comprising a slurrypreparation tank, esterification reactors of two stages connected inseries thereto and melt polycondensation tanks of three stages connectedin series to the second stage esterification reactor, terephthalic acidand ethylene glycol were continuously supplied in a weight ratio of865:485 to the slurry preparation tank, and a 0.3 wt % ethylene glycolsolution of ethyl acid phosphate, was continuously added in such anamount that the content as phosphorus atoms (P) per 1 ton of the formedpolyester resin would be 0.194 mol, followed by stirring and mixing toobtain a slurry. This slurry was transferred to the first stageesterification reactor set for an average retention time of 4 hours in anitrogen atmosphere at 260° C. under a relative pressure of 50 kPa (0.5kg/cm²G) and then to the second stage esterification reactor set for anaverage retention time of 1.5 hours in a nitrogen atmosphere at 260° C.under a relative pressure of 5 kPa (0.05 kg/cm²G), to carry out theesterification reaction. At that time, the average esterification ratioas measured by the following method, was 85% in the first stage and 95%in the second stage.

[0093] Average Esterification Ratio

[0094] With respect to a solution having a sample dissolved at aconcentration of 3 wt % in a mixed solvent of deuteratedchloroform/hexafluoroisopropanol (weight ratio: 7/3), ¹H-NMR wasmeasured by a nuclear magnetic resonance apparatus (“JNM-EX270 model”,manufactured by Nihon Denshi K.K.), and each peak was identified. Theamount of terminal carboxyl groups (A mol/ton sample) was calculatedfrom the integral value of the peak, and by the following formula, theesterification ratio (E %) was calculated as a proportion of theesterified among all carboxyl groups of terephthalic acid units.

Esterification ratio (E)=[1−A/{(1,000,000/192.2)×2}]×100

[0095] Further, at that time, via an upper pipe provided at the secondstage, a 0.6 wt % ethylene glycol solution of magnesium acetatetetrahydrate was continuously added in such an amount that the contentas magnesium atoms (Mg) per 1 ton of the formed polyester resin would be0.247 mol.

[0096] Continuously, at the time of transporting the esterificationreaction product obtained as described above to the meltpolycondensation tank, tetrabutyl titanate in the form of an ethyleneglycol solution having a concentration of titanium atoms of 0.15 wt %and a water concentration of 0.5 wt %, was continuously added to theesterification reaction product in the transportation pipe in such anamount that the content as titanium atoms (Ti) per 1 ton of the formedpolyester resin would be 0.063 mol, and the esterification reactionproduct was continuously transferred to the first stage meltpolycondensation tank set at 270° C. under an absolute pressure of 2.6kPa (20 Torr), then to the second stage melt polycondensation tank setat 278° C. under an absolute pressure of 0.5 kPa (4 Torr) and then tothe third stage melt polycondensation tank set at 280° C. under anabsolute pressure of 0.3 kPa (2 Torr), to carry out the meltpolycondensation for a total of 3.17 hours by adjusting the retentiontimes in the respective polycondensation tanks so that the intrinsicviscosity ([η₁]) of the obtained polyester resin would be 0.56 dl/g,whereupon the product is withdrawn in the form of a strand from adischarge outlet provided at the bottom of the polycondensation tank,cooled with water and then cut by a cutter to obtain a polyester resinin the form of chips.

[0097] Then, the polyester resin chips obtained as described above werecontinuously supplied for crystallization to an agitationcrystallization machine held at about 160° C. in a nitrogen atmosphereso that the retention time would be about 60 minutes and thencontinuously supplied to a tower type solid polycondensation apparatusand heated at 205° C. in a nitrogen atmosphere for 19 hours for solidphase polycondensation by adjusting the retention time so that theintrinsic viscosity ([η₂]) of the obtained polyester resin would be 0.75dl/g. The intrinsic viscosity ([η₁]) of the above melt polycondensateresin and the intrinsic viscosity ([η₂]) of the solid polycondensateresin, were measured by the above-mentioned method.

[0098] Further, the melt polycondensation rate (V₁) as a value obtainedby dividing the intrinsic viscosity ([η₁]) of the above meltpolycondensate resin by the melt polycondensation time, the solid phasepolycondensation rate (V₂) as a value obtained by dividing thedifference ([η₂]−[η₁]) between the above intrinsic viscosity ([η₂]) ofthe above solid polycondensate resin and the intrinsic viscosity ([η₁])of the above melt polycondensate resin, by the solid phasepolycondensation time, and the ratio (V₂/V₁) of the solid phasepolycondensation rate (V₂) to the melt polycondensation rate (V₁), werecalculated, respectively, and the results are shown in Table 2.

[0099] Further, with respect to the obtained solid phase polycondensateresin chips, the contents of titanium atoms (Ti), magnesium atoms (Mg)and phosphorus atoms (P) of the titanium component, the magnesiumcomponent and the phosphorus component, respectively, per 1 ton of theresin, were measured by the above-mentioned methods, and the results areshown in Table 2.

[0100] Further, with respect to the obtained solid phase polycondensateresin chips, the copolymerized amount of diethylene glycol, the cyclictrimer content (CT) and the color coordinate value b as the color tone,were measured by the above-mentioned methods, and the acetaldehydecontent (AA₁) was measured by the following method. The results areshown in Table 2.

[0101] Acetaldehyde Content (AA₁)

[0102] 5.0 g of a resin sample was accurately weighed and sealed intogether with 10 ml of pure water in a micro bomb having an internalcapacity of 50 mΩ under sealing with nitrogen, whereupon heat extractionwas carried out at 160° C. for 2 hours. The amount of acetaldehyde inthe extracted solution was quantitatively analyzed by gas chromatography(“GC-14A”, manufactured by Shimadzu Corporation) using isobutyl alcoholas the internal standard.

[0103] Then, the obtained resin was dried at 160° C. for 4 hours in anitrogen stream of 40 l/min in an inert oven (“IPHH-201 model”,manufactured by ESPEC COMPANY), and then, by an injection moldingmachine (“M-70AII-DM”, manufactured by Meiki Co., Ltd.), a steppedmolded plate having a shape shown in FIG. 1, was injection-molded at acylinder temperature of 280° C. under a back pressure of 5×10⁵ Pa at aninjection rate of 40 cc/sec under a dwell pressure of 35×10⁵ Pa at amold temperature of 25° C. with a molding cycle of about 75 seconds.

[0104] With respect to the molded plate, the absorbances at wavelengthsof 395 nm and 500 nm were measured by the above-mentioned method, andfurther, the acetaldehyde content (AA₂) and the haze, were measured bythe following methods. The results are shown in Table 2.

[0105] Acetaldehyde Content (AA₂)

[0106] Using samples cut out in the form of chips of about 4×4 mm fromthe rear end portion having a thickness of 3.5 mm (portion B in FIG. 1)in the molded plate, the measurement was carried out by the same methodas described above.

[0107] Haze

[0108] With respect to the portion having a thickness of 5.0 mm (portionC in FIG. 1) in the molded plate, the haze was measured by means of ahaze meter (“NDH-300A”, manufactured by NIPPON DENSHOKU INDUSTRIES CO.,LTD.).

[0109] Separately, the obtained polyester resin chips were dried at 130°C. for 10 hours in a vacuum dryer. Then, by an injection molding machine(“FE-80S”, manufactured by Nissei Plastic Industrial Co., Ltd.), apreform of a test tube shape having an outer diameter of 29.0 mm, aheight of 165 mm, an average wall thickness of 3.7 mm and a weight ofabout 60 g, was injection-molded at a cylinder temperature of 280° C.under a back pressure of 5×10⁵ Pa at an injection rate of 45 cc/secunder a dwell pressure of 30×10⁵ Pa at a mold temperature of 20° C. witha molding cycle of about 40 seconds.

[0110] The obtained preform was heated for 70 seconds in a near infraredray irradiation furnace equipped with a quartz heater and then left tostand at room temperature for 25 seconds. Then, it was introduced into ablow mold set at 130° C. and blow-molded under a blow pressure of 7×10⁵Pa for one second and further under a blow pressure of 30×10⁵ Pa for 5seconds, while stretching in the height direction by an stretching rod,heat-set and cooled in air to mold a bottle having an outer diameter ofabout 95 mm, a height of about 305 mm, an average wall thickness of thebody portion of about 0.35 mm, a weight of about 60 g and an internalcapacity of about 1.5Q.

[0111] With respect to the obtained bottle, the aroma-retention propertyand the mold contamination were measured and evaluated by theabove-mentioned methods, and further, the acetaldehyde odor wasevaluated by the following method. The results are shown in Table 2.

[0112] Acetaldehyde Odor of the Bottle

[0113] The bottle was heated in an oven at 50° C. for one hour,whereupon the acetaldehyde odor was examined by a sensory test andevaluated by five stages ranging from 5 (acetaldehyde odor very little)to 1 (acetaldehyde odor assails ones nostrils).

EXAMPLES 10 TO 23, AND COMPARATIVE EXAMPLES 5 TO 7

[0114] Polyester resin chips were prepared in the same manner as inExample 9 except that the copolymerizable component and its amount, theamounts and order for addition of the phosphorus compound, the magnesiumcompound and the titanium compound, the concentration of titanium atomsand the water concentration in the ethylene glycol solution of thetitanium compound, and the melt polycondensation time and the solidphase polycondensation time, were changed as identified in Table 2, andevaluated in the same manner. The results are shown in Table 2. InComparative Example 5, phosphorous acid instead of ethyl acid phosphate,cobalt acetate tetrahydrate instead of magnesium acetate tetrahydrateand titanium potassium oxalate instead of tetrabutyl titanate, were usedand added in the order of titanium potassium oxalate, then cobaltacetate tetrahydrate and then phosphorous acid. In Comparative Example7, orthophosphoric acid was used instead of ethyl acid phosphate, andthe order of addition was tetrabutyl titanate, then magnesium acetatetetrahydrate and then orthophosphoric acid. TABLE 2 Examples 9 10 11 1213 14 15 16 17 Copolymer- Diethylene glycol 2.2 2.2 2.2 2.2 2.2 2.2 1.72.2 2.2 izable (mol % based on diol) components Isophthalic acid 1.8(mol % based on dicarboxylic acid) Ethylene Concentration of titanium(wt %) 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.40 0.15 glycol atomssolution of Water concentration (wt %) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 1.50.03 the titanium compound Contents of Titanium atoms (T) (mol/t) 0.0630.063 0.063 0.063 0.063 0.125 0.063 0.063 0.063 metal atoms Magnesiumatoms (M) (mol/t) 0.247 0.123 0.370 0.247 0.247 0.247 0.247 0.247 0.247Cobalt atoms (M) (mol/t) Phosphorus atoms (P) (mol/t) 0.194 0.194 0.1940.065 0.387 0.387 0.194 0.194 0.194 P/T (mol/mol) 3.1 3.1 3.1 1.0 6.23.1 3.1 3.1 3.1 M/T (mol/mol) 3.9 2.0 5.9 3.9 3.9 2.0 3.9 3.9 3.9 Poly-Melt polycondensation time (hr) 3.17 3.33 3.00 3.00 3.33 3.00 3.17 3.253.25 condensation Intrinsic viscosity [η₁] (dl/g) 0.56 0.56 0.56 0.560.56 0.56 0.56 0.56 0.56 rate Polycondensation rate (dl/g/hr) 0.1770.168 0.187 0.187 0.168 0.187 0.177 0.172 0.172 (V₁) Solid phasepolycondensation (hr) 19 20 22 18 28 18 18 20 20 time Intrinsicviscosity [η₂] (dl/g) 0.75 0.75 0.75 0.77 0.77 0.76 0.75 0.75 0.75Polycondensation rate (V₂) (dl/g/hr) 0.010 0.010 0.009 0.012 0.008 0.0110.011 0.010 0.010 V₂/V₁ 0.057 0.060 0.046 0.063 0.045 0.060 0.060 0.0550.055 Resin chips Acetaldehyde content (AA₁) (ppm) 3 4 4 3 4 4 3 4 4Cyclic trimer content (CT) (wt %) 0.28 0.28 0.32 0.24 0.24 0.19 0.270.28 0.28 Color coordinate b +2.2 +2.4 +2.2 +3.4 +2.4 +4.7 +2.2 +2.4+2.4 Stepped Absorbance 395 nm 0.16 0.14 0.16 0.20 0.15 0.26 0.16 0.160.16 molded plate 500 nm 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02Acetaldehyde content (AA₂) (ppm) 16 18 15 20 14 20 14 16 16 Haze (%) 7 88 8 7 8 4 12 15 Bottle Aroma-retention property ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Moldcontamination property ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Acetaldehyde odor 4 4 4 4 5 4 54 4 Comparative Examples Examples 18 19 20 21 22 23 5 6 7 Copolymer-Diethylene glycol 2.2 2.2 2.2 2.2 2.2 2.2 3.1 2.8 3.8 izable (mol %based on diol) components Isophthalic acid (mol % based on dicarboxylicacid) Ethylene Concentration of titanium (wt %) 0.15 0.15 0.15 0.15 0.150.15 0.15 0.15 0.15 glycol atoms solution of Water concentration (wt %)0.5 0.5 0.5 0.5 0.5 0.5 0.03 0.03 0.03 the titanium compound Contents ofTitanium atoms (T) (mol/t) 0.010 0.313 0.063 0.063 0.063 0.063 0.1250.021 1.086 metal atoms Magnesium atoms (Mg) (mol/t) 0.247 0.247 0.7400.247 0.247 1.550 2.180 Cobalt atoms (M) (mol/t) 1.033 Phosphorus atoms(P) (mol/t) 0.387 0.387 0.194 0.194 0.775 0.494 1.070 0.549 P/T(mol/mol) 37.1 1.2 3.1 3.1 0 12.4 3.95 1.2 0.5 M/T (mol/mol) 23.6 0.8 011.7 3.9 3.9 8.37 74.2 2.0 Poly- Melt polycondensation time (hr) 4.002.00 3.67 2.75 2.83 4.00 3.50 3.50 2.00 condensation Intrinsic viscosity[η₁] (dl/g) 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 0.56 ratePolycondensation rate (dl/g/hr) 0.140 0.280 0.153 0.204 0.198 0.1400.160 0.160 0.280 (V₁) Solid phase polycondensation (hr) 38 12 26 32 1542 43 42 12 time Intrinsic viscosity [η₂] (dl/g) 0.76 0.76 0.75 0.750.77 0.77 0.75 0.75 0.75 Polycondensation rate (V₂) (dl/g/hr) 0.0050.017 0.007 0.006 0.014 0.005 0.004 0.005 0.016 V₂/V₁ 0.038 0.060 0.0480.029 0.071 0.036 0.028 0.029 0.057 Resin chips Acetaldehyde content(AA₁) (ppm) 4 11 4 4 3 4 8 3 11 Cyclic trimer content (CT) (wt %) 0.550.17 0.28 0.56 0.21 0.45 0.88 0.49 0.34 Color coordinate b +0.6 +11.3+2.4 +2.4 +4.2 +2.4 −2.3 +2.2 +14.3 Stepped Absorbance 395 nm 0.09 0.310.20 0.21 0.27 0.10 0.06 0.06 0.42 molded plate 500 nm 0.01 0.05 0.030.03 0.04 0.02 0.01 0.01 0.06 Acetaldehyde content (AA₂) (ppm) 18 30 2114 28 13 27 23 35 Haze (%) 7 12 9 8 12 7 8 8 70 Bottle Aroma-retentionproperty ◯ ◯ ◯ ◯ ◯ ◯ X ◯ X Mold contamination property ◯ ◯ ◯ ◯ ◯ ◯ X ◯ XAcetaldehyde odor 4 1 3 5 2 5 2 3 1

INDUSTRIAL APPLICABILITY

[0115] According to the present invention, it is possible to provide apolyester resin, whereby a molded product excellent in a gas barrierproperty and also excellent in an ultraviolet shielding property, colortone, etc., and which is particularly suitable for molding a bottle fore.g. a beverage required to have an aroma-retention property and furtherto provide a polyester resin, whereby the acetaldehyde content in amolded product is reduced to eliminate an influence over the taste,aroma, etc. of the content, and a process for its production, wherebythe polycondensability is improved.

1. A polyester resin produced by polycondensing a dicarboxylic acidcomponent containing terephthalic acid or its ester-forming derivativeas the main component, and a diol component containing ethylene glycolas the main component in the presence of (1) a compound of at least onemember selected from the group consisting of titanium group elements inGroup 4A of the periodic table, via an esterification reaction or anester exchange reaction, characterized in that the content ofcopolymerized components other than the terephthalic acid component andthe ethylene glycol component, is not more than 4 mol % based on thetotal dicarboxylic acid component, and in a molded product with athickness of 3.5 mm injection-molded at 280° C., the difference betweenthe absorbance at a wavelength of 395 nm and the absorbance at awavelength of 800 nm is at least 0.08, and the difference between theabsorbance at a wavelength of 500 nm and the absorbance at a wavelengthof 800 nm is at most 0.05.
 2. The polyester resin according to claim 1,wherein the temperature-rising crystallization temperature (Tc) of theresin in the molded product after the injection molding at 280° C., isfrom 150 to 180° C.
 3. The polyester resin according to claim 1, whereinthe resin before the injection molding is one having an intrinsicviscosity ([η]) of from 0.70 to 0.90 dl/g and a color coordinate value bof the Hunter's color difference formula of not more than
 4. 4. Thepolyester resin according to claim 1, wherein the content of thecompound (1) is from 0.002 to 1 mol as the total amount (T) of atoms ofthe compound (1) per 1 ton of the polyester resin.
 5. The polyesterresin according to claim 4, which is one polycondensed in thecoexistence of (2) a compound of at least one element selected from thegroup consisting of metal elements of Group Ia of the periodic table,elements of Group IIa of the periodic table, manganese, iron and cobalt,and (3) a phosphorus compound, wherein the content of the compound (2)is from 0.04 to 5 mols as the total amount (M) of atoms of the compound(2) per 1 ton of the polyester resin, and the content of the compound(3) is from 0.02 to 4 mols as the total amount (P) of atoms of thecompound (3) per 1 ton of the polyester resin.
 6. The polyester resinaccording to claim 5, wherein the contents of the respective compounds(1), (2) and (3) are from 0.02 to 0.2 mol as the total amount (T) ofatoms of the compound (1), from 0.04 to 0.6 mol as the total amount (M)of atoms of the compound (2) and from 0.02 to 0.4 mol as the totalamount (P) of atoms of the compound (3), per 1 ton of the polyesterresin, the acetaldehyde content (AA₁) is not more than 5.0 ppm, theacetaldehyde content (AA₂) of the resin in a molded product afterinjection-molded at 280° C. is not more than 20 ppm, and the haze of amolded product with a thickness of 5 mm after the injection molding at280° C. is not more than 10%.
 7. The polyester resin according to claim1, wherein the compound (1) is a titanium compound, the compound (2) isa magnesium compound, and the compound (3) is a phosphoric acid ester.8. The polyester resin according to claim 1, wherein, as a dicarboxylicacid component, from 0.1 to 3 mol % of isophthalic acid or itsester-forming derivative based on the total dicarboxylic acid component,and as a diol component, from 1 to 3 mol % of diethylene glycol based onthe total diol component, are copolymerized, respectively.
 9. A processfor producing a polyester resin, which comprises polycondensing adicarboxylic acid component containing terephthalic acid or itsester-forming derivative as the main component, and a diol componentcontaining ethylene glycol as the main component in the presence of (1)a compound of at least one member selected from the group consisting oftitanium group elements in Group 4A of the periodic table, (2) acompound of at least one element selected from the group consisting ofmetal elements of Group Ia of the periodic table, elements of Group IIaof the periodic table, manganese, iron and cobalt, and (3) a phosphoruscompound, via an esterification reaction or an ester exchange reaction,characterized in that the amounts of the respective compounds (1), (2)and (3) are such amounts that their contents will be from 0.02 to 0.2mol as the total amount (T) of atoms of the compound (1), from 0.04 to0.6 mol as the total amount (M) of atoms of the compound (2) and from0.02 to 0.4 mol as the total amount (P) of atoms of the compound (3),per 1 ton of the polyester resin.
 10. The process for producing apolyester resin according to claim 9, wherein the ratio (P/T) of thetotal amount (P) of atoms of the compound (3) to the total amount (T) ofatoms of the compound (1), is from 0.1 to
 10. 11. The process forproducing a polyester resin according to claim 9, wherein the ratio(M/T) of the total amount (M) of atoms of the compound (2) to the totalamount (T) of atoms of the compound (1), is from 0.1 to
 10. 12. Theprocess for producing a polyester resin according to claim 9, whereinthe order for addition of the respective compounds (1), (2) and (3) tothe reaction system is (3), then (2) and then (1).
 13. The process forproducing a polyester resin according to claim 9, wherein the compound(1) is a titanium compound, the compound (2) is a magnesium compound,and the compound (3) is a phosphoric acid ester.
 14. The process forproducing a polyester resin according to claim 13, wherein the titaniumcompound is added to the reaction system in the form of an ethyleneglycol solution having a titanium atom concentration of from 0.01 to 0.3wt % and a water concentration of from 0.1 to 1 wt %.
 15. The processfor producing a polyester resin according to claim 9, wherein from 0.1to 3 mol % of isophthalic acid or its ester-forming derivative is usedbased on the total dicarboxylic acid component.